1. Field of the Invention
The present invention relates generally to a method to reduce or remove fibrosis following glaucoma surgery involving administration of purified collagenase into a patient's eye.
2. Description of the Related Art
Glaucoma is a leading cause of irreversible blindness. About 60.5 million people were affected with glaucoma in 2010, with a predicted increase to approximately 79.6 million by 2020. Approximately fourteen percent of those affected with glaucoma will be bilaterally blinded. Treatments that lower intraocular pressure are common for control of glaucoma, regardless of the type of glaucoma. When medications or lasers cannot effectively control or lower the intraocular pressure to acceptable levels, surgical intervention is often necessary.
Glaucoma filtration surgery, i.e., trabeculectomy, is a commonly performed type of glaucoma surgery. In glaucoma filtration surgery, a small opening, i.e., a fistula, is created between an anterior chamber of an eye and the subconjunctival and sub-Tenon's space of the eye. Aqueous fluid produced by the eye is thereby given an alternative pathway to leave the eye, lowering intraocular pressure.
As a result of glaucoma filtration surgery, however, scarring and fibrosis develops at the subconjunctival and sub-Tenon's tissues. Scarring and fibrosis develops following collagen deposition in the area of the glaucoma filtration surgery. The scarring and fibrosis often results in a gradual reduction of filtration and loss of control of intraocular pressure. Moreover, surgical failures occur in up to 30% of cases. Histologic examination of filtration operations resulting in scarring has shown that obstruction to filtration occurs at the subconjunctival tissues including the Tenons capsule and episcleral tissues. Multiple efforts aimed at improving the healing process have been attempted.
Pharmaceutical agents including steroids, such as Tissue Plasminogen Activator (TPA); Betaaminopropionitrile (BAPN); D-penicillamine; daunorubicin; 5-fluorouracil; and Mitomycin C, have been used in an effort to prevent fibrosis following surgery. However, failures readily occur with such agents.
Mechanical devices, such as metallic shunts and collagen inserts, have also been used to improve healing from glaucoma filtration surgery. Other interventions such as radiation have also been attempted. However, mechanical devices have also been unsuccessful in preventing fibrosis and reduction of filtration.
When glaucoma filtration fails, seton implants are often used to help form a mechanical barrier to prevent formation of scar tissue. However, seton implants are also subject to wound healing after implantation and failure of these devices readily occurs. Failure of seton implants is also due to formation of fibrous scar tissue surrounding the implant, which prevents adequate drainage of aqueous fluid.